1. Field of the Invention
The present invention relates to communication systems. More specifically, the present invention relates to inexpensive, expendable power supplies for low power radio frequency transmitters.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
In many applications, there is a need for an inexpensive power supply for a low power radio frequency transmitter. For example, in military applications, the conventional technique for determining the ability of a gunner to hit a target with a projectile is visual. That is, the target is simply visually examined to determine the number of hits and, hence, the score of the gunner.
Unfortunately, the visual scoring method is costly due to the requirement that the target be retrieved and examined to provide a score. Visual scoring from a remote location is often complicated by numerous range and/or battlefield conditions including darkness, haze, smoke, dust, and etc. In addition, there is no real time feedback of a gunners score during the firing operation. Accordingly, the opportunity for real time correction is not provided with conventional scoring techniques.
U.S. patent application entitled RADIO FREQUENCY DEVICE, FOR MARKING MUNITION IMPACT POINT, Ser. No. 07/798,480, filed Nov. 26, 1991, by J. O. Muirhead and G. E. Held discloses a unique and advantageous automatic system for gunnery scoring. The system includes a plurality of miniature radio transmitters which are mounted on one or more of the projectiles. The transmitters are energized when the projectile impacts the target. The transmitted signal is detected by one or more receivers. Detection occurs when the received signal exceeds a fixed threshold. By accurately monitoring the time of arrival at a number of different locations, the angle of arrival may be determined at each receiver from which the impact point of the round can be determined by triangulation.
When widely separated receivers are used, the difference between the times of arrival of the radio frequency (RF) energy at any pair or receivers defines a hyperbolic line of position which is the locus of all points which have that difference in distance from the pair of receivers. The use of three (or more) receivers will define three (or more) lines of position. Where these lines intersect is the origin of the RF energy in the plane of the system.
When closely spaced receivers are used, the difference between times of arrival between the receivers and the distance between the receivers define the direction from which the energy arrived at the pair. With two or more pairs of receivers at known locations distant from the impact area, the location of the origin of the RF energy can be determined. The use of wide beam, directional antennas eliminates ambiguity in location of the RF emission source.
In any event, since the energy for the transmitter is generated by the impact of the projectile with the target, the amount of electrical energy available to the transmitter oscillator varies in accordance with the hardness of impact points for different objects and the angle at which the projectile strikes the object. This produces differing decelerations and therefore differing amounts of electrical current into the transmitter oscillator. The amount of energy into the transmitter determines the amount of energy radiated by the transmitter. Accordingly, the energy of the signals radiated by the transmitters of this system varies considerably from round to round. This complicates detection and scoring.
Thus, a need remains for an improved power supply for radio frequency (RF) projectiles which provides a consistent amount of radiated power on impact with soft as well as hard objects.